1. Field of the Invention
The present invention generally relates to an oil separator provided between a compressor and a refrigerator to separate oil contained in a refrigerant gas.
2. Description of the Related Art
Examples of a regenerative type refrigerator can include a Gifford-McMahon cycle refrigerator (a GM refrigerator), a Joule-Thomson refrigerator plus a GM refrigerator, a closed cycle refrigerator, and a Stirling refrigerator. Among these, the GM refrigerator is frequently used. The GM refrigerator is connected to a compressor. By adiabatically expanding a high-pressure refrigerant gas supplied from the compressor inside the refrigerator so that the high pressure refrigerant gas has a low pressure, cold thermal energy is generated in the refrigerant gas. By accumulating the generated cold thermal energy in a regenerative material, an ultralow temperature is obtainable.
The compressor is provided to increase the pressure of the low-pressure refrigerant gas returned from the GM refrigerator, i.e., a return gas, by its compressor body, and supply the return gas again to the refrigerator. The pressure of the return gas returned from the GM refrigerator is raised again by the compressor body and then the refrigerant gas is cooled using a refrigerant gas heat exchanging unit.
After the cooling process is performed, the refrigerant gas supplied from the compressor is sent to the oil separator and the oil is separated. An example of the oil separator is disclosed in Japanese Laid-open Patent Publication No. 2008-39222. The refrigerant gas from which the oil is separated is sent to an adsorber and is supplied as a supply gas to the GM refrigerator.
The oil separator includes a shell and a filter element. The shell includes an upper flange, a lower flange and a cylindrical portion. The filter element includes a filter member for catching oil contained in the refrigerant gas, an upper lid bonded to an upper portion of the filter member, a lower lid bonded to a lower portion of the filter member and a gas inlet pipe for introducing the refrigerant gas inside the filter member.